This print reproduces the final version of The Nightmare, created by Fuseli in the last months of his life but now lost. It resembles the painting shown by Fuseli at the Royal Academy in 1782, although the owl and the vain fairies on the left are new additions. Prints like this helped ensure that Fuseli's image continued to be wellknown.

With the encouragement of the painter and astrologer John Varley (1788-1842), Blake produced a series of 'visionary heads' recording the features of imaginary and historical characters said to have visited him. This drawing represents the bloodthirsty spirit of a flea. Varley took the fact that Blake drew both a whole face, and the detail of the mouth, as evidence of the concrete nature of these visions.

This weird image was said to have been inspired by a vision. The scaly creature is meant to be the ghost of a flea. He appears, as if on a stage, holding an acorn cup and a thorn. Like Fuseli's The Nightmare, Blake's painting seems to incorporate a range of references to folklore, science and literature. Blake may have had the evil imp of Fuseli's painting in mind when he painted this picture.